Lecture 22: Beef Nutrition 2

Cold stress _____ energy requirements beyond maintenance.

increases

What BCS should cows be going into winter?

5-6

What do NRC factors need to account for?

• Amount of body fat = insulation

• Heat production from feed

  • Forages → more heat production

  • Grains → higher energy density increase heat production on poor quality forage diets

What is the target BCS for beef cows at breeding and calving?

5-7

BCS reflects ____ preserves.

fat

How does BCS affect time to first estrus in beef cattle?

shorter interval to first heat with higher BCS

How does BCS affect colostrum quality and calf immunity in beef cattle?

• Colostrum quality → higher with higher cow BCS

• Calf immunity → higher IgG levels for calves born to cows with higher BCS

Why is BCS a better indicator of performance than BW in ruminants?

because BWchanges in gut fill

How does low or high BCS affect pregnancy rate?

decreases it

What is the target BW for heifers at breeding and calving?

• Target 65% BW at breeding

• Target 85% BW at calving

What is the most important factor affecting puberty?

BW

What is preconditioning of weaned calves?

• Process to reduce stress and improve health before feedlot entry

• Strategy to reduce health issues in the feedlot, improve growth post-weaning, and enhance overall profit

What are the preconditioning components?

• health & welfare: castration, dehorning, deworming

• vx: two sets of MLV and clostridial vx

• bunk training: feed and using water troughs

What should be done prior to shipping calves?

30-45 day low-stress weaning (use fence line weaning)

What is a value-added calf?

• Preconditioned

• Individual ID

• Source/age verified

• Proper injection practices (in front of shoulder to decrease muscle site blemishes)

• Typical return = >$30/calf

When is energy supplementation needed?

• ADG > 0.5 lbs/d

• With low quality hay

• Winter or late summer

What should the level of CP be in the overall diet of growing stocker cattle?

12-16%

Why is UIP often needed for stockers?

to ensure that some essential AA reach animal

What supplement should not be used with high forage diets because of the slow digestion, but can be used with high energy diets?

urea

What nutrient limits growth on low-quality forage?

protein

What are the risks of high grain diets in feedlots?

• Risk of acidosis

• Laminitis

• Liver abscesses

What is the goal of transitioning to a feedlot diet?

• adapt rumen microbes to new substrate: forage → grain (needs to occur over 3-4 wks)

• maintain intake

• prevent acidosis (slow adjustments)

What is the diet adaptation strategy for transitioning to feedlot?

• Start: 60% forage / 40% concentrate

• End: 90% concentrate

• Key point: Gradual transition prevents rumen upset

What are the important aspects of feedbunk management?

• Consistency is key (fresh feed delivered on time)

• Monitor intake

• Feed ad libitum, but minimize waste (want a little feed left to ensure cattle are eating all they can)

How can grain cause urinary calculi?

grain high in P → upsets Ca:P ratio

What can cause nitrate toxicity in cattle?

• pasture fertilization → plants accumulate nitrates

• weeds

What can cause sulfur toxicity in cattle?

distiller’s grains (causes sulfur-associated polioencephalomalacia)

What causes sulfur-associated polioencephalomalacia?

high dietary sulfur → increases metabolic demand for thiamine → results in secondary thiamine deficiency

Trenbolone acetate has _____ properties.

androgenic

Hormonal implants increase ____ by 15-20%.

ADG

What is MGA (melengestrol acetate)?

• progesterone analog

• suppresses estrus (decrease DMI) in heifers

How are beta-agonists used for cattle growth?

repartitioning agent → more muscle deposition

What is the purpose of ionophores?

• mechanism: shift rumen fermentation, modify rumen microbes, decrease acetate and methane, increase proprionate

• direct metabolism towards deposition of muscle instead of fat

What are the benefits of ionophores?

increased feed efficiency and decreased acidosis